The San Gabriel Fault is a geological fault in

Los Angeles County, California Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the most populous county in the United States and in the U.S. state of California, with 9,861,224 residents estimated as of 2022. It is th ...

, running about southeastward from the Ridge Basin in the Sierra Pelona- San Emigdio Mountains juncture area to the western

San Gabriel Mountains The San Gabriel Mountains ( es, Sierra de San Gabriel) are a mountain range located in northern Los Angeles County and western San Bernardino County, California, United States. The mountain range is part of the Transverse Ranges and lies between ...

that forms their southwestern face near Sunland and the northeastern San Fernando Valley, and then on the south flank to the southeastern part of the San Gabriel range.

Geology

The San Gabriel Fault is a right-lateral strike-slip that was last active thousands of years ago — Late Quaternary west of intersection with the Sierra Madre Fault, and Quaternary east of that intersection, and

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

only further west between Saugus and

Castaic Castaic () ( Chumash: ''Kaštiq''; Spanish: ''Castéc'') is an unincorporated community in the northwestern part of Los Angeles County, California. As of the 2010 census it had a population of 19,015. For statistical purposes the Census Bure ...

- Gorman. The San Gabriel Fault was once part of the

San Andreas Fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizontal) ...

, and is believed to be the former path of it. It is also believed that the northwestern end of this fault zone meets the current San Andreas Fault zone beneath the

Frazier Mountain Frazier Mountain ( Samala: ''Toshololo'') is a broad, pine-forested peak in the Transverse Ranges System, within the Los Padres National Forest in northeastern Ventura County, California. At , Frazier Mnt. is the sixteenth-highest mountain in the ...

Thrust, near the juncture of the San Andreas with the Garlock Fault and Big Pine Fault.San Gabriel fault zone/faultmaps
The San Gabriel Fault moves at a rate of between 1 and 5 millimeters a year, with an average slip of around 3 millimeters.

References

External links

– USGS

– Southern California Earthquake Data Center
Geoscienceworld.org: San Gabriel Fault
{{California Faults Seismic faults of California San Gabriel Mountains Strike-slip faults Geology of Los Angeles County, California Geography of the San Fernando Valley Natural history of Los Angeles County, California